1. Field of the Invention
The present invention relates to an anti-after-burning system applicable to an industrial engine provided with a governor device.
2. Description of the Prior Art
An engine stopping and controlling system disclosed in Japanese Utility Model Publication No. 1-28282 (1989) will be explained with reference to FIGS. 9 to 13 as one example of an anti-after-burning system in the prior art. FIG. 9 is a front view of an engine directly coupled to a rotary machine. FIG. 10 is a front view of an anti-after-burning system. FIG. 11 is a schematic plan view of the system showing the state where a throttle is set on a high-speed side. FIG. 12 is a schematic plan view of the system showing the state where a throttle is held on a low-speed side as a result of the excitation of a solenoid when no load is on the engine. And, FIG. 13 is a schematic plan view of the system showing the state of a plunger once the engine has been stopped, a stop button has been press-actuated, and the plunger has been retracted while having moved a throttle to a low-speed side.
In these figures, reference numeral 11 designates the engine, numeral 12 designates the rotary machine such as an electric generator, a welding machine or the like which is directly coupled to the engine, numeral 13 designates an air cleaner, numeral 14 designates a carburetor, and numeral 15 designates a governor mechanism. The governor mechanism includes a governor spring 19 stretched between a governor control lever 18 and a governor lever 17 pivotably supported by a governor shaft 16. One end of this governor lever 17 and a throttle lever 20 of the carburetor 14 are connected by means of a governor rod 22 wound by a rod spring 21. In this illustrated engine, the resilient force exerted by the governor spring 19, generated owing to the rotational position of the above-mentioned governor control lever 18, biases the governor lever 17 to a high-speed side. Consequently, the throttle lever 20 is normally set at the high-speed side. In addition, reference numeral 23 designates a solenoid powered by an engine charging coil (in the case where the rotary machine driven by the engine is an electric generator, the solenoid could be powered by the electric generator). The solenoid 23 is provided with a plunger 24 that is free to move except when the solenoid is excited. This plunger 24 is connected to the governor lever 17 directly or via a rod 25. When the engine 11 is not loaded, the plunger 24 is retracted under the excitation of solenoid 23 and the governor lever 17 and the throttle lever 20 having been set at the high-speed side are moved to the low-speed side. It is to be noted that while the plunger 24 is free to move when the solenoid is not excited in the illustrated engine, an internally contained spring could be provided in the solenoid 23 to normally bias the plunger 24 forwards.
The above-described engine is provided with a stoppage switch 26 for stopping the engine. This stoppage switch 26 has a contact connected via a cable to a primary wire of an ignition circuit and a ground side contact provided within a main body 27. A contact piece is provided on a bottom surface of a switch actuator 28 which extends through an aperture in the main body 27. Thus, the switch 26 is adapted to be turned on or off by the contact or separation of this contact piece with or from the above-mentioned contacts. The switch actuator 28 is biased in a direction of separation by means of a return spring 29 contained within the main body 27. In addition, the actuator 28 of the above-mentioned switch 26 has a holding rod 30 projecting from the bottom surface of the main body 27. The holding rod 30 is projected and retracted through the bottom surface of the main body 27 when the main body is slid in an approaching direction upon the press-actuation of the actuator 28 and is slid in the separating direction under the biasing force exerted by the return spring 29, respectively. This stoppage switch 26 is mounted by bracket 31 in the proximity of the outer circumference of the plunger 24 of the solenoid 23 when the plunger is in its extended state. A holding groove 32 for receiving the holding rod 30 is formed circumferentially or in a spotted pattern on the outer circumference of the plunger 24. The groove 32 becomes opposed to the tip end of the holding rod 30 of the above-mentioned switch actuator 28 when the plunger 24 has been attracted under the excitation of the solenoid 23 upon no loading of the engine. When the engine stops (upon no loading), the holding rod 30 is engageably inserted into the holding groove 32 of the plunger 24, and while the switch actuator 28 is being press-actuated, the retracted state of the plunger 24 can be maintained against the resilient force of the governor spring 19 even if the solenoid 23 is demagnetized.
Upon loading of the engine 11, as shown in FIG. 11, the solenoid 23 is in a demagnetized condition, so that the governor lever 17 is swung by the governor control lever 18 and the governor spring 19 so as to set the throttle lever 20 to the high-speed side. On the other hand, upon no loading of the engine 11, as shown in FIG. 12, the solenoid 23 is excited through an electric wiring (not shown) and retracts the plunger 24 against the resilient force of the governor spring 19 which was set on the aforementioned high-speed side, whereby the governor lever 17 and the throttle lever 20 are moved to the low-speed side. Upon stoppage of the engine, after the above-described no load condition shown in FIG. 12 has been established, the switch actuator 28 is pressed against the force exerted by the return spring 29, and as a result of its contact piece coming into contact with the respective contacts of the ignition circuit primary wire and the ground side, the ignition circuit primary wire is grounded. At this time the solenoid 23 having retracted and the plunger 24 had been demagnetized. However, due to the pressed state of the switch actuator 28, the holding rod 30 projects into the holding groove 32 on the outer circumference of the plunger 24 as shown in FIG. 13. Therefore, while the switch actuator 28 is kept in the pressed condition, the plunger 24, the governor lever 17 and the throttle lever 20 can be maintained on the low-speed side against the resilient force of the governor spring 19. Accordingly, the above-described arrangement can preclude the disadvantage that occurs upon the stoppage of an engine, when the output of the engine 11 gradually decreases and the solenoid 23 which has retracted the plunger 24 to the low-speed side against the biasing force of the governor spring 19 is demagnetized. That is, in spite of additional rotational output by the engine (ignition plugs are not sparking) unnecessary fuel will not be sucked in great quantities because the governor lever 17 and the throttle lever 20 have not returned to the high-speed side.
However, the above-described anti-after-burning system in the prior art involves the following problems. That is, due to the fact that a solenoid is utilized in order to prevent an excessive suctioning of fuel after the feeding of electric energy to the engine has been terminated, an electric energy source for exciting the solenoid is necessary. Accordingly, the above-described system is applicable only to an engine provided with a battery or an engine-driven type electric generator, and it cannot be applied to an engine not having an electric energy source.